1. Field of the Invention (Technical Field)
The present invention relates to task chairs that support the body of the user in healthy positions while the user performs various tasks over extended sitting periods and that provide independent and independently adjustable support to the lower and the upper back.
2. Description of Related Art
Note that the following discussion refers to a number of publications by author(s) and year of publication, and that due to recent publication dates certain publications are not to be considered as prior art vis-a-vis the present invention. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
Today, the average worker performs less physical activity and workers perform increasingly more of their work while in a seated position. It is known that if any part of person's anatomical function is impinged or static (i.e., remaining in a fixed position) for extended periods of time, posture and health are compromised. It has been determined that both physically active and physically inactive people suffer health problems caused by prolonged sitting. Those problems include lower back pain, muscle tension, numbness, acid reflux, carpel tunnel syndrome, and general fatigue.
Peter Escogue, a recognized expert in anatomical function, suggests these problems are posture related as well as inactivity related. Proper anatomical posture promotes proper anatomical function, i.e. the body functions best when operated from a proper position. Escogue further observes that over a period of time, many persons compromise correct posture causing problems in correct anatomical function.
Static, improper posture (e.g., while sitting in a static improper supporting chair) impairs good health. In the prior art, seats and chairs have been designed for comfort and for performing tasks. Task chairs were designed to incorporate pads, tilts, swivels, etc. Over time, health improvements were added to the combination of such items as family room recliners and workers' rigid elevating stools. Additions such as lumbar supports, adjustable armrests, seat backs with shapes designed for a general vertebrae contour, etc., were incorporated. However, today's combination task chairs offer few features to accommodate multiple tasks while simultaneously giving adequate consideration to seating health.
Task chairs are typically configured to allow tilting of the seat and backrest as a unit or tilting of the backrest relative to the seat. In chairs having a backrest pivotally attached to a seat in a conventional manner, the movement of the backrest relative to the seat can create shear forces acting on the legs and back of the user. These shear forces tend to cause an uncomfortable pulling of the user's clothing. In an attempt to compensate for these shear forces, some office chairs include a backrest which pivots while the seat tilts, such as those disclosed in U.S. Pat. Nos. 2,859,801 (to Moore) and U.S. Pat. No. 4,429,917 (to Diffrient).
A related disadvantage of conventional task chairs is the configuration of the seat and/or backrest. Such seats typically include single or multi-density foam padding with a covering such as cloth, leather, mesh material or the like, such seating also tends to provide insufficient aeration since it acts as another layer of clothing and does not contain a spinal relief channel in the back support, and/or contain a coccyx relief in the horizontal seat. In addition, the structural requirements of such an attachment limits the shape and size of the frame and the membrane.
Typically, the seats of office task chairs are supported by a single stage telescoping column which provides for vertical adjustment of the seat. These columns include a gas spring mounted in a telescoping tube which is slidable within a base tube. In accordance with guidelines set by the American National Standards Institute (A.N.S.I.) and Business and Institutional Furniture Manufacturer's Association (B.I.F.M.A.), conventional office chairs in the United States are typically adjustable from a seat height of 16.0 inches from a floor to about 20.5 inches from a floor. Nevertheless, it is desirable to exceed this range of height adjustment to account for very small or large users and to accommodate the international population in general.
Typically, it is difficult to exceed this range of height adjustment with seats which tilt about the knees or ankles of the user. To offset the moments acting on single stage support columns, pneumatic manufacturers typically set a minimum overlapping distance of 2.95 inches (75 mm) between the tubes. Because such “ankle tilt” and “knee tilt” chairs have relatively large tilt housings, it is difficult to provide a lower minimum and higher maximum seat height while maintaining the required overlapping distance between the tubes. These types of tilting chairs also impart a greater moment on the tube since the pivot axis is offset from the support column. It is therefore desirable to provide a vertically adjustable support column having a greater overlapping distance to permit a greater stroke which decreases the minimum height and increases the maximum height of a chair seat.
Devices that incorporate a plurality of adjustable means have been disclosed in the prior art such as, for example, U.S. Pat. Nos. 6,478,379 (to Ambasz) and 6,189,971 (to Witzig). However, those devices do not allow for the independent adjustment of multiple, vertical backrest support arms.
Other patents disclose the use of various seat and back units incorporating means for altering the contour of the pads used on such seats such as, for example, U.S. Pat. Nos. 6,499,802 (to Drira) and 6,447,061 (to Klingler). However, these devices do not allow for the independent adjustment of multiple, vertical backrest support arms.
Although offering varying shapes, contours, masses and sizes, as well as a wide range of adjustment means i.e. pivotal, tilt, height, in/out, up/down, soft/firm, etc., all attempts at healthy task chairs in the prior art are burdened with an interdependent posterior design support which ultimately restricts and compromises adjustability, dynamic support, and active seating. A chair that provides better posterior support and continuous animation, and better supports task functions, is thus needed.